Monte Carlo Simulation of DNA Damage Induction by
X-rays and Selected Radioisotopes

Y. Hsiao and R. D. Stewart
Phys. Med. Biol. 53(7), 233-244 (2008)
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To better assess the potential biological consequences of diagnostic x-rays and selected g-emitting radioisotopes used in brachytherapy, we used the PENELOPE Monte Carlo radiation transport code to estimate the spectrum of initial electrons produced by photons in single cells and in an irradiation geometry similar to the ones used in cell culture experiments.  We then combined estimates of the initial spectrum of electrons from PENELOPE with DNA damage yields for monoenergetic electrons from the fast Monte Carlo damage simulation (MCDS). The predicted absolute yields (Gbp^-1 Gy^-1) and RBE  values for single strand break (SSB) and double strand break (DSB) induction by 220 kVp x-rays are within 1% of the results from detailed track-structure simulations (Friedland et al. 1999). The measured RBE for DSB induction reported by Kühne et al. (2005) for g-rays from ⁶⁰Co and for 29 kVp x-rays with a 50-µm Rh (mammography) filter are in excellent agreement (1.15 vs 1.16).  DSB yields predicted by the MCDS also agree to within 7% with the absolute DSB yields reported by de Lara et al. (2001) and Botchway et al. (1997) for the irradiation of V79 cells by low energy (< 2 keV) characteristic x-rays. The predicted RBE for DSB induction by g-rays from bare ¹⁶⁹Yb and ¹³¹Cs to ⁶⁰Co are 1.06 and 1.14, respectively. Tabulated RBE values for the single-cell and monolayer cell culture geometries differ by at most 15%.  The proposed methodology is computationally efficient and may also be useful for the prediction of damage yields for mixtures of other types of charged particles, such as the ones found in proton therapy, space applications or internal dosimetry.

Acknowledgements

The authors thank Dr. Frank Verhaegen for helpful discussions and suggestions on the manuscript.
 

Last updated: January 14, 2013